Hydraulic fracturing refers to a process in which a wellbore is drilled into a rock formation, and a fracturing fluid is then pumped into the wellbore under great pressure to induce an initial set of fractures in the rock formation. The fracturing fluid is then forced into the initial fractures, extending the fractures further. An operator may then introduce a proppant into the fracturing fluid that is being pumped into the fractures, such as sand, ceramic particles to other particulates. The proppant is designed to prevent the fractures from closing when the fracturing fluid pressure is reduced or when pumping stops.
Once the fracturing process is complete, petroleum, natural gas and other fluids which are under considerable pressure in the rock formation escape through the fractures and into the wellbore. The petroleum and natural gas is ultimately extracted through the fractures and the wellbore and is captured and stored. During the initial stages after the fracturing is completed, the petroleum and natural gas may push much of the fracturing fluid back up the well bore. However, it is also common for a significant percentage of the fracturing fluid to disperse into the surrounding rock through the fractures that were created.
The fracturing fluid which is pumped into the wellbore typically includes water. However, various chemicals and materials are added to the water for various purposes. The chemicals that are added can depend upon the type of well and the underground rock formations that are being fractured. In addition to the proppants mentioned above, friction reducing additives can be used to increase the flow rate and to reduce the pressure needed to pump the fracturing fluid into the well. Oxygen scavengers and other stabilizers and corrosion inhibitors can be added to prevent corrosion of the pipes. Acid, such as hydrochloric acid, can be added to help dissolve minerals and induce fractures. Surfactants and crosslinking agents help to maintain fluid viscosity, particularly as temperature increases. Gels can be added to help suspend greater amounts of proppants in the fracturing fluid. A scale inhibitor may be added to prevent scale deposits in the pipes. A pH adjusting agent may be added to maintain the effectiveness of the other agents, particularly the crosslinkers. Finally, various biocides may be added to eliminate bacteria which can produce corrosive byproducts that attack the pipes. The biocides that are added to fracturing fluid can include glutaraldehyde, quaternary amines, active liquid brominated propionamide solutions and other materials. It is important that any biocide added to the fracturing fluid not disrupt or inhibit the functions performed by the other additives.
Because the fracturing fluid can escape into the surrounding rock formations, and ultimately propagate into the water table, there is great concern about the chemical additives that are present in the fracturing fluid. Thus, operators are seeking to use chemicals which are known to be safe to humans, animals and the environment.